Δ24 (25)-sterol methenyltransferase: Intracellular localization and azasterol sensitivity in Leishmania major promastigotes overexpressing the enzyme

Instituto de Parasitología y Biomedicina López-Neyra, Consejo Superior de Investigaciones Científicas, Parque Tecnológico de Ciencias de la Salud, Avenida del Conocimiento, s/n 18100 Armilla, Granada, Spain.
Molecular and Biochemical Parasitology (Impact Factor: 1.79). 08/2008; 160(1):52-9. DOI: 10.1016/j.molbiopara.2008.03.010
Source: PubMed


Trypanosomatids contain predominantly ergostane-based sterols, which differ from cholesterol, the main sterol in mammalian cells, in the presence of a methyl group in the 24 position. The methylation is initiated by S-adenosyl-L-methionine:Delta(24 (25))-sterol methenyltransferase, an enzyme present in protozoa, but absent in mammals. The importance of this enzyme is underscored by its potential as a drug target in the treatment of the leishmaniases. Here, we report studies concerning the intracellular distribution of sterol methenyltransferase in Leishmania major promastigotes and overexpressing cells using a specific antibody raised against highly purified recombinant protein. It was found by immunofluorescence and electron microscopy studies that in L. major wild-type cells sterol methenyltransferase was primarily associated to the endoplasmic reticulum. In addition to this location, the protein was incorporated into translucent vesicles presumably of the endocytic pathway. We also found in this study that cells overproducing the enzyme do not have increased resistance to the sterol methenyltransferase inhibitor 22, 26 azasterol.

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    • "The methylation is initiated by S-adenosyl-L-methionine: Delta (24 (25))-sterol methenyltransferase, an enzyme present in protozoa, but absent in mammals. The importance of this enzyme is underscored by its potential as a drug target in the treatment of the leishmaniasis [106]. The C-24 transmethylation reactions involving S-adenosyl-L-methionine as the methyl donor and a Δ24(25)-sterol or Δ24(24′)-sterol substrate can be inhibited by various azasterols with a nitrogen substitution in the side chain and such compounds have been tested against trypanosomatids [107]. "
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